AC vs. DC Power: Why Are They Different?

In the 1880s, a historic battle between Edison’s direct current (DC) and Tesla’s alternating current (AC) was taking place. This AC vs. DC event decided which type of current would be used to power the world. Ultimately Tesla’s AC stood victorious despite Edison’s cruel ploys to discredit AC.

Before the event took place, DC was the only current people could generate at the time. It was simple, sufficiently capable, and was the industry standard. So why replace it with AC? Why the need to develop a new current? And how does one differ from the other?

Let’s find out!

What Is Direct Current?

DC or direct current is the type of current where electric charge flows in only one direction.

Direct current is primarily sourced from DC generators such as solar panels and permanent magnet motors. You can also store it in batteries like the popular 18650s, AA, and AAA. As well as be converted from AC with rectifiers such as a bridge rectifier installed on a phone charger.

Batteries can only store currents that flow in one direction. This means that all conventional batteries can only store direct current and not alternating current.

With that in mind, you can easily distinguish what devices use DC, whether a phone, a laptop, wireless earphones, or a camera. As long as it uses a battery, DC powers it.


What Is Alternating Current?

Alternating Current is the type of current where electric charge flows back and forth. This means that half of the time, the current is positive, and half of the time, it is negative, hence the name alternating current.

Alternating currents are generated through mechanical generators such as steam turbines, windmills, and combustion engines. You can also source alternating currents from DC through rectifying components such as an inverter on your portable battery backups or battery generators. Because of the continuously changing polarity of AC, no battery is yet to store alternating current successfully.

Alternating current is the preferred current for power transmission from power plants to your house. Since no rectification is done from the distribution lines to your home, all electrical outlets and sockets inside your house are AC powered. This means that all appliances plugged into an electrical outlet (washing machine, blender, refrigerator) use AC.

Now that you can differentiate AC from DC, let us answer the big question—why are they different? If DC was simple, sufficiently capable, and was the industry standard before AC, why the need for a new current type?

Why Are AC and DC Different?

AC and DC are two different types of Current. DC flows in one direction, while AC alternately flows back and forth.

The constant unidirectional flow of a DC provides stable electricity favorable for powering electronics and storing power in batteries. The downside of DC is its inefficient power transfers through long distances.

DC was generated with high currents (amps) at low voltages (volts). Transferring high currents at a slow place (due to low pressure or voltage) allows heat to build up in the transmission wires, which wastes a lot of energy. This would also mean that transmission cables needed to be thicker to dissipate heat. Because of this, electricity providers needed a better way of transferring energy.

The solution was to transfer smaller amounts of Current at high voltages to negate heat build-up while also transferring more power. This is where AC becomes essential. The alternating back and forth flow of electrons in AC allows magnets to produce strong electromagnetism in an alternator to function. With an alternator, power plants could easily convert high currents at low voltages to low currents at high voltages.

Basically, AC and DC are different because the industry needed a current that allows easy conversion for long-distance power transmissions.

Both Currents Are Important

AC and DC are currents that make up the modern world. AC is used for long-distance power transmissions and powering power-hungry factories. DC is used to power electronics such as phones, cameras, and computers.

Although AC won the war of currents, it doesn’t necessarily mean it is better than DC. AC is better used for long-distance power transmissions and high-power applications in homes, factories, and other establishments. In contrast, DC is better used for storing power in batteries and low-power applications in electronics.

We should stop comparing AC and DC. Both currents have their pros and cons. And none of them is better than the other. Because at the end of the day, there isn’t a better current, only a better application for a specific current.

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